Exercise 5: Simple Data Exploration
Geographic Information Systems 1 Lab

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The purpose of this exercise is to help familiarize you with simple ways to explore attributes in various datasets. These skills will help you extract new datasets, connect to tabular data, and qualitatively compare different variables.

1 The Introduction

With the unprecedented growth in middle Tennessee, the Montgomery County Commission, Stormwater Management, and Health Department are working with the Tennessee Department of Environment and Conservation on an initiative to assess the relationship of brownfield sites to our community and watersheds. Brownfields are locations in communities that pose risks to future land use and development as a result of previous land use practices, particularly commercial and industrial (check out more information on brownfields here: https://www.osha.gov/brownfields/brownfields-qna). They often contain high levels of soil and water contamination, and in some cases pollutants can remain in the ecosystem for decades. Unfortunately, brownfields are often point source locations for ground and surface water contamination. The goal of the initiative is to determine if there are any spatial characteristics of these hazardous locations that have the potential to impact current and future residents of the area. The primary objectives of the initative are to: a) examine the location of brownfields in the county, b) determine which watersheds would be primarily impacted, and c) ascertain if there is a relationship between brownfield sites and any particular demographics in teh county. With these three objectives, the county partners may make data-informed decisions to best support and prioritize programs that keep our community and environment safe.

In this exercise you will:

• Continue working with geoprocessing tools
• Obtain and import data from external sources
• Learn to link tabular data
• Qualitatively compare datasets

Software specific directions can be found for each step below. Please submit the answer to the questions and your final map by the due date.

1.1 Step One: The Data

The datasets used in this exercise will be found on the Exercise 5 Github Page, previous exercises such as Exercise 2 and Exercise 3, and also from the Tennessee Geographic Information Council. TN GIS maintains a number of datasets in their collections that are useful for projects involving the state of Tennessee.

View Directions in ArcGIS Pro

As with previous exercises you should begin by launching ArcGIS Pro, creating a new blank template, and creating a folder for this specific exercise. You should now see the typical starting screen that greeted you in all of the previous exercises. While some of the data you may already have in previous exercise folders, you will start his lab by downloading a dataset from TN GIS. While they maintain a number of quality collections, you will specifically download the statewide watershed coverage (12 digit Hydrologic Unit Code) for Tennessee. This information can be found at the following link: http://www.tngis.org/water.htm. On that page you will find the link for “Download Watershed Coverage”. Click the link, and using the download button in the upper-right corner, save the tn_wbd zip file to your project folder.

Once you have downloaded the file, navigate to the saved location to unzip the file. Within the unzipped folder you will find three additional folders titled:

• tn_8dig_huc
• tn_12dig_huc
• tn_250k_huc

These are watershed files at varying levels of detail. For hydrologic units you are looking for one with the largest number of digits to get the largest scale data. So for this exercise you will unzip the tn_12dig_huc dataset.

Finally, with that final folder extracted you will find a folder titled hydrologic_units that will contain a shapefile named wbdhu12_a_tn.shp that will be used in this exercise. This is the polygon file representing the 12 digit hydrologic unit codes for the entire state of Tennessee.

Next, you will need the tornado_data file from Exercise 2 and the census_tracts data from Exercise 3. You have a few options for obtaining this data. You can download the data again (but this time to the new project folder), you can navigate to the Exercise 2 and Exercise 3 project folders, respectively, on your computer and copy the zip files to the Exercise 5 project folder, or you can copy the data over using the catalog pane in ArcGIS Pro. While the first two options are relatively straight forward, it is important to learn how to navigate and use the catalog in ArcGIS.

On the View tab, click the Catalog Pane button to open the Catalog Window Pane on the right side of the screen. On the project tab, right-click on the folders option and click "Add Folder Connection. In the resulting window navigate to the folder you would like to connect to and single-click the folder to select it. You don’t want to double-click into the folder. You should see the name of the folder appear at the bottom of the window and the OK button should be available.

Once you have connected to the additional folders you want to use in conjunction with this project you can navigate to them within the Folders link in the Catalog Pane. While you could add data directly from the other folders, the best practice might be to copy the data from one project to another. If for example you plan to alter the data then using it directly from the previous folder would alter it there as well. This could cause future issues when returning to that project. For this exercise you can navigate to the Exercise 2 folder and copy the tornado_data file and paste it in the Exercise 5 folder. This is the safest way to move data such as shapefiles or geodatabases. Because the various data types contain numerous individual files to make up a dataset, catalog will copy/move them all correctly. If you tried to move them using File Explorer and missed one of the files associated with that data it might not work appropriately. So for Exercise 5, you will need to copy the tornado_data and montco_tracts data from exercises two and three respectively.

Finally, you will need to download the Brownfields and Demographics data from the Exercise 5, GitHub Data page. Save both in your Exercise 5 project folder and unzip the brownfields.zip file to access the dataset.

Question No. 1
Using File Explorer, examine the dataset contained in the brownfields.zip file and answer the following question:

What is the common name of the extracted files? How many are there? What are the various file extensions?

The library of Congress has a great description of the various extensions here.

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View directions in QGIS

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View directions in R

Before you begin, you will need to open the Ex2 Colab Notebook and insert tocolab after github in the URL to open in the Colab Environment. As you have seen before, R requires various packages to complete certain analyses. In this exercise you will be using tidyverse, OpenStreetMaps, ggfortify, maptools, and rgeos. To install and load the packages we will use the following script:

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Question No. 1

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1.2 Step Two: The Analyses

The data collected in the previous section requires additional processing so you can reduce the dataset to only the pertinent information for the analyses. In this step you will use additional geoprocessing techniques and data management tools to link two datasets for further examination.

View Directions in ArcGIS Pro

With the data collected you can now add the brownfields, census tracts, tornado_data, and wbdhu12_a_tn (watersheds) data to your project. Although there are a number of ways of isolating data to make derived datasets (e.g. Select > Lasso in Exercise 4, Step 1, in this exercise you will use another tool from the Geoprocessing Toolbox to complete this task. On the View Tab click on the Geoprocessing Toolbox button to open the Geoprocessing pane on the right side of the screen. By navigating through the tools menus you will find Select under Analysis Tools > Extract. With this tool you will write a simple expression to “select” a small portion of the data you need for further analysis. To do this, double-click the Select tool and in the resulting pane input the following parameters:

• Input Features = tornado_data
• Output Feature Class = Here you will insert the file name you want to use. Click on the folder icon to the right of the field and in the new window save the file as montgomery_county.shp in your project folder.
• Expression = Click the drop-down button for the new expression button and use the drop-down boxes to provide the following information:
  • Where NAME   is equal to   Montgomery
  • Click Run

This will add the new montgomery_county shapefile to your contents. You can now remove the tornado dataset because it will no longer be needed. With the outline of Montgomery County now available you can now use the Clip tool like in Exercise 4, Step One to clip the brownfields and watersheds datasets to reduce them to only those within Montgomery County. If you receive a “Datum conflict” warning, for the purposes of this exercise, you can ignore it an continue with the clip. Recall that the Input Features is the data you want to reduce, the Clip Feature is the data you want it to take the shape of, and Output Feature Class is what you are naming the new file.

With the new clipped datasets you can remove or just uncheck (in case you want to use them in your final map) the full brownfields and watersheds datasets to reduce clutter. You can also now zoom in closer to view only Montgomery County.

In the final step to prepare the data, you are going to connect a non-spatial data to the census tract dataset. In Step One you downloaded a file titled demographics.csv. This file contains comma-separated values detailing additional demographic data that you need to append to the census tract data. Although the process is relatively straight-forward, there are a number of steps that need to be taken in order to join the data.

First, if you haven’t already, add the demographics.csv file to your table of contents. This can be done from the Catalog Pane or with the “Add Data” button like in previous exercises.

Question No. 2

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View Directions in R

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1.3 Step Three: The Visualization

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View directions in R

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1.4 Step Four: The Proposal

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Question No. 4

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Question No. 4

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2 The Write-Up

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When complete, send a link to your Colab Notebook or word document with answers to Questions 1-4 and your completed map via email.